[1.12.2] Crash when shift+left clicking a gas tank into a gas level emitter filter.

[ncaycedo]

Hey! There seems to be a problem with the gas level emitter GUI.

Steps to reproduce:

1. Install a gas level emitter in your network.
2. Open level emitter GUI.
3. Shift+Left Click a tank containing some gas to filter.

here's the crash report: https://pastebin.com/cq1phCW6

cheers!